Vapor permeable synthetic leather products



1968 HIDEO MATSUSHITA ETAL 3,399,102

VAPOR vPERMI EPABLIE SYNTHETIC LEATHER PRODUCTS Filed Jan. 9, 1967 INVENTORS H IDEO MAT 5U SHITA ICH 1R0 MINOBE YOSHAKI SAKATA United States Patent 6 3,399,102 VAPOR PERMEABLE SYNTHETIC LEATHER PRODUCTS Hideo Matsushita, Itami, and Ichiro Minobe and Yoshiaki Sakata, Osaka, Japan, assignors to The Toyo Rub- 5 her Industry Co., Ltd., Osaka, Japan Continuation-impart of application Ser. No. 377,077, June 22, 1964. This application Jan. 9, 1967, Ser. No. 608,166 Claims priority, application Japan, Dec. 27, 1963, 38/70,432 3 Claims. (Cl. 161-64) ABSTRACT OF THE DISCLOSURE A synthetic leather product is provided. A web of random fibers is placed on a fabric designed for napping. A composite is needled from the web side to unite the web layer with the fabric layer. The fabric layer is napped to obtain a napped surface having a higher fabric density than that of the web layer. The napped surface is coated with a solvent solution of a polyurethane polymer. The polymer is coagulated by immersing the coating in a nonsolvent for the polymer.

The specification This application is a continuation-in-part of application Ser. No. 377,077, filed June 22, 1964 and now abandoned.

The present invention relates to a vapor permeable synthetic leather and to the multi-layer base material employed in the manufacturing of such a synthetic leather product.

The demand for a synthetically produced material which can be utilized in the same manner as natural leather is Well known in the art. Particularly vapor-permeable synthetic leather products are desirable since these materials may be utilized in certain instances Where such vapor permeability is essential, as for example, in the 40 production of shoe uppers. The present invention is designed to provide such a vapor permeable synthetic leather material.

A base material utilized in preparing synthetic leather must have certain characteristics. It is required to have a fibrous roughness on its outer surface. It is also required to have a texture corresponding to the collagen tissue found in natural leather. The base material of the synthetic leather must be coated with a resinous substance to form a surface corresponding to the epidermis of natural leather. The fibrous roughness of the base material when coated with the resinous substance provides the surface corresponding to the epidermis of natural leather. It is also necessary that the base material provide a layer of appropriate thickness to form the layer corresponding to the corium layer of natural leather. The prior art methods have failed to provide a synthetic leather meeting the requirements of a true leather substitute.

It is an object of the present invention to provide a synthetic leather possessing the attributes of a true substitute for natural leather.

It is also an object of the present invention to provide a multi-layer base material to be used in the preparation of such synthetic leather as well as a method for the preparation of such multi-layer base material.

It is a further an object of the present invention to provide a synthetic leather having the handle and drapeability of natural leather.

Additional objects will be apparent from the description of the invention set forth herein.

The multi-layer base employed in producing the syn- 3,399,102 Patented Aug. 27, 1968 'ice thetic leather of the present invention is formed by placing a random web or card web on one surface of a fabric from the group of woven or knitted fabrics, which fabrics are designed for napping, as for example flannel or suede fabrics. The two layers are then non-adhesively united by needling with barbed needles from the web side. This causes the web fibers to pass into the knitted or woven fabric and firmly unites the two layers. Between the woven or knitted fabric and the web it is permissible O to insert an unwoven cloth or, alternatively, an additional woven or knitted fabric may be introduced therebetween. The amount of web material which is united to the woven or knitted fabric should be preferably above grams per square meter (g./m. The needling density should be such that the web becomes mat-like and must be sufiicient to unite the web to the woven or knitted fabric. Accordingly, the needling density is preferably above 100 times per square centimeter (times/cm?) Following the needling operation, the fabric surface is subjected to a napping treatment. The napping treatment may be carried out in the same manner as when flannel, suede or napped tricot fabrics are subjected to a napping treatment and for this method a teasel napping machine or a metal wire napping machine can be employed. The frequency of napping is that Which is suflicient to obtain a napped surface on the fabric side having a higher fiber density than that of the web layer.

In this manner, a base material is produced having a density gradient in its thickness direction which is similar to the texture of natural leather. The frequency of the napping process is from 3 to 10 times depending upon the desired surface. The napped surface can, if necessary, be sheared in the same manner as woven or knitted fabrics.

As indicated above, the woven or knitted fabric employed must be one which is designed for napping, as for example suede or fiannel. It is impossible to obtain the object of the present invention by utilizing a coarse woven fabric in the process. If such materials are used, an insufficiently dense pile or nap is obtained. In accordance with the present invention, a dense pile is obtained and the density difference among the various layers achieves the production of a leather-like product.

The uniting of the web to the fabric to produce the base material is, as indicated, a non-adhesive process. The present invention does not employ a coating step to anchor the web to the fabric, as in previously employed processes for producing synthetic leathers. To do this is harmful to the ultimately produced product. In the event such adhesive joining is employed, a product having the handle and drapeability of natural leather is not achieved. However, in accordance with the method of the present invention, such natural leatherlike characteristics are obtained.

With respect to the napping step employed, it is important in conjunction with the present invention that the napping step be with regard to the woven fabric. In certain previously conducted processes the fibers of a bat are forced through a coarse woven fabric and subsequently these fibers are combed to straighten them out, causing them to lie in the same direction, i.e. substantially parallel to each other land at right angles to the coarse fabric employed. Such a process is not identical to that conducted in the present invention. In the present invention the woven or knitted fabric is itself napped, thus enabling the production of a material obtained having the characteristics of a natural leather product due to the fact that the density gradient of the material is more similar to that of natural leather.

The multilayer base material is then coated with a solvent solution of a polyurethane-urea polymer. This polymer is prepared by the reaction of polyalkylene ether glycol or polyester glycol with a molar excess of organic polyisocyanate to produce a prepolymer having terminated isocyanate groups. This is followed by a chain extending the prepolymer with organic diamines, such as ethylene diamine. Such polymers are themselves well known in the art. The polymer solution may be applied to the napped surface of the base material, as for example by a coating method. The polymer in the solution is then coagulated by treating with a non-solvent for the polymer to remove the solvent. This can be done, for example, by immersing the material in the non-solvent. The product may then be dried and, if desired, the surface coated with a coating agent. In addition, the surface may be heated and pressed at a temperature above the softening point but below the melting point of the polymer, thereby producing a synthetic leather product having the desired characteristics. The heating temperature and the pressure employed in such finishing steps may be appropriately selected depending upon the kinds of polymer treated and the desired feel to be possessed by the synthetic leather product. For example, in the case of a segmented polyurea polymer which is prepared by reacting polypropylene ether glycol With a molar excess of toluene diisocyanate to produce anisocyanate terminated prepolymer and subsequently chain extending said prepolymer, the melting point of the polymer will be 200 C., 188 C. and 186 C. respectively, according to the respective molecular weights of 700, 100 and 2000. The appropriate heating conditions in such case would be 160 to 180 C., 145 to 165 C. and 140 to 160 C. respectively.

A polymer which is obtained by chain extending the prepolymer prepared by the reaction of polyethylene glycol with a molar excess of toulene diisocyanate and having terminal isocyanate groups, with a polyamide (molecular weight: 5000) prepared by a reaction of ccaprolactam with hexamethylene diamine hydrochloride, has a melting point of about 180 to 215 C., although the melting point varies depending upon the reaction weight ratio of the polyamide to prepolymer. However, in the case of higher melting point, it would be necessary to heat up to about 165 to 190 C.

In general, the optimum pressure exerted on the polymer coating would be about 0.5 to 3 kilograms per square centimeter (kg./cm.

The synthetic leather product of the present invention which is thus obtained has a natural leather-like appearance and feel. It has desirable drapeability and flexibility. In particular, it provides natural leather-like fine break, which is important for use in the material as shoe uppers.

Having thus described the present invention, it will be illustrated with reference to the appended drawing and the following example, which are merely illustrative and not to be taken as exhaustive of the present invention.

Example 1 On one surface of a plain woven cotton fabric, having a tissue of 20 x 46/inch in warp, and loosely twisted yarn of 20 x SO/inch in woof, are placed random webs, consisting of 1.5 denier 51 mm. rayon staple fibre, in the amount of 350 g./m. and from the web side, needling is carried out by barbed needles. The density of the needling is about 200 times/cm? Then, the sheet, thus obtained, has its cotton fabric side napped by a metal wire napping machine for cotton fiannel napping. Napping process is carried out five times at a speed of 7 m. per minute and, moreover, the napped surface is sheared to a napping length of about 2 mm. by means of a shearing machine.

The sheet thus obtained is useful as a synthetic leather base material having a smoothened napped surface and a plain woven tissue beneath same and, furthermore, a corium layer of irregularly entangled fibres.

The base material was impregnated in a solution of 10 parts of linear polyurethane dissolved in parts of N,N-dimethyl formamide so as to be coated with said polyurethane in an amount of 400 g./m. the said polyurethane compound being prepared by chain extending an isocyanate terminated prepolymer from 1 mol of polypropylene ether glycol having an average molecular weight of about 1000 and 2 mol of 2,4 toluene diisocyanate, with ethylene diamine, and then the said impregnated base material was immersed in an excess of water to coagulate the urethane polymer. After washing in water and drying, the napped surface side was pressed at a pressure of 3 kg./cm. at a temperature of C., thereby producing a synthetic leather.

Relating the synthetic leather, thus produced, to the appended drawing, the corresponding components of the product are as follows:

(1) random webs, consisting of 1.5 denier 51 mm. staple fibre.

(2) plain woven cotton fabric.

(3) napped cotton fabric.

(4-) urethane polymer coating.

Combined components 1, 2 and 3 constitute the base ma terial.

The synthetic leather, thus produced, has a thickness of about 1.9 mm., is soft and pliable, and its surface condition and handling when bent is very similar to natural leather.

This synthetic leather may further be given a coating treatment on its napped surface either before or after the heating and pressing treatment or, by dyeing or bufiing on the web side, it may be made to appear more like natural leather.

The synthetic leather, thus prepared, may be used for bags or shoe uppers. Especially as a material for shoe upper, it has a superior processability in shoe making, as compared with the conventional base material made from woven fabrics. This is because of the fact that directional dependence of mechanical properties of woven fabric is reduced by the random fibers of the web and, accordingly, the synthetic leather, thus obtained, is an amendable to shoe-making processing as is a natural leather.

Having thus disclosed the invention, what is claimed 1. A multi-layer base material for use in the preparation of a vapor'permeable synthetic leather product which comprises a reinforcing fabric layer selected from the group of woven and knitted fabric designed for napping, said fabric layer being non-adhesively united to a web layer by needling and the outer surface of the fabric layer being napped and the nap having a fiber density greater than the needled web layer.

2. A multi-layer base material in accordance with claim 1, wherein the fabric layer is non-adhesively united to the web layer by needling with barbed needles.

3. A vapor permeable synthetic leather product which comprises a coagulated polyurethane-urea polymer surface layer coated on the napped surface of the multi-layer base material of claim 1.

References Cited UNITED STATES PATENTS 1,406,710 2/1922 Wilson 117-4 1,825,827 10/1931 Smith 161-67 XR 2,485,967 10/1949 Harding 156-241 3,100,721 8/1963 Holden 2872.2 XR 3,214,819 11/ 1965 Guerin 2872.2

ROBERT F. BURNETT, Primary Examiner.

R. L. MAY, Assistant Examiner. 

